On Tue, Aug 6, 2013, at 11:51 AM, Andrew wrote: > 2013/8/6 andy pugh <[email protected]> > > > The problem is that the travel distance isn't accurate. A 50mm move is > > out by 0.158mm. The encoder scale is set to 25600 (10um scales, 256 > > interpolation). > > > > Is it always 0.158 or it changes with the lenght? Let him try it slow and > fast etc. >
I agree with Andy - he needs to do some methodical checks. To accurately measure distance error, I suggest putting a 50mm (or whatever) gage block between the indicator and the reference surface, record the reading, remove the block, move till the indicator directly touches the reference surface, and record the reading again. Repeat at half the speed and maybe even 1/10th the speed, to see if the error is constant with velocity. Repeat with a significantly shorter gage block (like 2mm) to see if the error is linear. Also repeat with as long a distance as possible, full axis travel or something close. He's unlikely to have 300mm of gage blocks, but a 300mm steel rule could be used if the ends are actually 300mm apart. If he really had 70um over 2mm and 158um over 50mm, it is very non-linear. In that case, I'd be looking for things that happen during direction reversals, etc. If it is more like 6um at 2mm and 150um at 50mm, then that would indicate a scale error of some sort - consistently 3um per mm of travel. -- John Kasunich [email protected] ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
